1. Field of the Invention
The present invention relates to lithium-manganese oxides or lithium-manganese metal oxides, a method of preparing the same, and lithium adsorbent using the same; and more particularly, to lithium-manganese oxides or lithium-manganese metal oxides, and a method of preparing the same that can be used as a precursor of lithium adsorbent or material of a secondary battery.
The present invention was deduced from researches performed as one of marine research and development projects of Ministry of Maritime Affairs and Fisheries [Task Management No. GFB20010004, Project Title: The Development of Technology for Recovering the Valuable Minerals from Seawater and Sand].
2. Description of Related Art
Technologies for recovering useful metals or minerals from seawater may be classified into technologies for collecting useful metals from seawater, and technologies for economical collecting systems. Researches on technologies for recovering various useful metals including lithium existing in seawater have been performed for about 30 years. As a result, while researches for recovering a small amount of useful metals have been performed, the technologies cannot be commercialized. Useful metal recovering technologies researched and developed up to now are known to include an adsorption method, a coprecipitation method, a solvent extraction method, an ion flotation method, an ion exchange method, a bioconcentration method, and so on. Among the above methods, the adsorption method has highest probability of commercial utilization.
Adsorbent used for the adsorption method may be classified into inorganic adsorbent and organic adsorbent. The adsorbent is required to provide high adsorption performance and selectivity, rapid adsorption speed, high physical strength, and good chemical stability and durability.
In particular, in selective adsorption of lithium, lithium-manganese oxides and lithium-transition metal oxides including transition metal having structure capable of intercalation and deintercalation of lithium ions are used as a precursor of lithium adsorbent. In addition, since lithium-manganese oxides or lithium-metal oxides have spinel and layered network structure to smoothly perform intercalation and deintercalation of lithium ions, the oxides can be used as active materials of electrodes for a lithium secondary battery.
The lithium-manganese oxides or lithium-transition metal oxides having the layered structure, for example, LiMnO2, LiCoO2, LiNiO2, and so on, have R-3m structure that lithium, oxygen and transition metal element alternately form the layered structure. Viewing LiMnO2 as an example of the lithium-transition metal oxides with reference to FIG. 1, manganese ions exist between oxygen ions having hexagonal closed packing, i.e., octahedral site of oxygen ions, and lithium ions exist octahedral site thereunder (see FIG. 1A). When lithium ions are inserted into the compound to form Li2MnO2 structure, a manganese ion layer exists, an oxygen ion layer exists under the manganese ion layer, a lithium layer is disposed to form a multi-layer, another oxygen layer exist under the lithium layer, and another manganese ion layer exist thereunder (see FIG. 1B). Such reversible intercalation and deintercalation of lithium ions enables lithium-transition metal oxides having the layered structure to be used as a precursor of adsorbent of lithium ions and electrode materials of a lithium secondary battery.
However, in conventional lithium-manganese oxides or lithium manganese oxides including transition metals, intercalation and deintercalation of lithium ions are more effectively and smoothly performed to improve lithium adsorption performance and selectivity. In addition, there is still need for materials that can be used as a precursor of lithium adsorbent and active materials of electrodes of a lithium secondary battery having better physical strength and chemical stability.